Question: If $x \oplus y = x-5y$ and $x \triangleright y = xy+2x-y$, find $0 \oplus (4 \triangleright -5)$.
First, find $4 \triangleright -5$ $ 4 \triangleright -5 = (4)(-5)+(2)(4)-(-5)$ $ \hphantom{4 \triangleright -5} = -7$ Now, find $0 \oplus -7$ $ 0 \oplus -7 = 0-(5)(-7)$ $ \hphantom{0 \oplus -7} = 35$.